Anatomy Flashcards
Tell me about carotid sinus baroreceptors
carotid sinus baroreceptors:
-stretch receptors that control HR & BP through feedback loops. (stretch receptors, nor pressure)
-location: internal carotid artery distal to the carotid bifurcation and carotid body (the latter lies at the bifurcation).
-Similar baroreceptors are found in the aortic arch, atria & left ventricle.
-nerve supply: carotid sinus nerve, which is a branch of the ninth cranial nerve (glossopharyngeal) receives afferent fibres from the carotid sinus and carotid body and ascends to the vasomotor centre.
As the distending pressure in the artery increases, the discharge rate from the baroreceptors increases, which stimulates the cardioinhibitory centre, causing a fall in blood pressure, heart rate and cardiac output.
In chronic hypertension, in order to maintain an elevated blood pressure, the reflex mechanism is reversibly reset.
effects of hyperoxia & hypoxia on CBF
hyperoxia reduces CBF. This is marked under hyperbaric conditions.
-hypoxaemia increases CBF
-Below a PaO2 of around 7-8kPa CBF rises sharply. Above this value a gentle slope downwards is seen, with a reduction in CBF of around 10% with an FiO2 of 1.0
CBF
1.what is normal CBF
2. effect of GA on CBF
3. effect of ketamine on CBF
4. effect of lower plasma viscosity is associated with enhanced blood flow
1.54ml/100g/min
2. General anaesthesia is associated with a rise in CBF secondary to vasodilation.
3. Ketamine increases cerebral metabolic rate and hence blood flow.
4. Lower plasma viscosity is associated with enhanced blood flow
relationship between PaCO2 and CBF
There is a linear relationship between PaCO2 and CBF from around 3.5-10.0 kPa. At 10kPa CBF is around 120 ml/100g.
Which nerve passes through the supraorbital fissure?
The lacrimal nerve, a branch of opthalmic nerve which branches from trigeminal nerve CNV
what are the different zones of the lung
1-16= conducting zones (gas exchange not taking place)
17-23 = respiratory zone (where gas exchange occurs- bronchioles to alveoli)
what does foramen ovale in fetus do?
What happens at birth
Foramen ovale creates right to left shunt from right atrium to left atrium, bypassing the lungs and going directly into systemic circulation
At birth, lung expansion reduces pulmonary vascular resistance, allowing blood to flow into lungs. Oxygen causes pulmonary vasodilation, further decreasing PVR and increasing pulmonary blood flow.
- clamping of cord eliminates placental circulation causing increased SVR. This results in higher LA pressure, helping close the foramen ovale.
what does ductus venosus do and what happens at birth
ductus venosus bypasses liver. (blood from umbilical vein enters ductus venosus directing blood into IVC and bypassing the liver. It closes when placental flow stops
what does ductus arteriosus do and what happens at birth
DA= PA-> aorta
The in utero fetus has high PVR and low SVR.
ductus arteriosus
A large portion of RV output is shunted from pulmonary artery to the aorta via the ductus arteriosus, further bypassing the fetal lungs.
At birth, DA closes due to increased oxygen levels and reduced prostaglandin E2 (PGE2). Functional closure occurs within hours, and anatomical occurs within days.
PDA causes left to right shunting, causing pulmonary congestion and heart faikure if significant. Prostaglandin inhibitors (eg indomethaicn) can help close a PDA
name the cranial nerves and what is the mneumonic
What is a characteristic of a lesion of the femoral nerve (L234)?
Weakness of the quadriceps femoris muscle, loss of sensation over the front of the thigh, loss of the knee jerk
The weakness of the quadriceps leads to weakness of extension of the knee.
What is supplied by the lateral cutaneous nerve of the thigh (L1,2)?
Skin on the lateral aspect of the thigh and knee, lower lateral quadrant of the buttock
This nerve primarily provides sensory innervation.
Which muscle group is innervated by the obturator nerve (L2-4)?
Adductors of the hip
The obturator nerve also supplies sensation to the inner part of the thigh.
Fill in the blank: A lesion of the femoral nerve is associated with loss of sensation over the _______.
front of the thigh
True or False: The lateral cutaneous nerve of the thigh provides motor function to the thigh muscles.
False
It primarily provides sensory innervation.
What sensory area does the obturator nerve supply?
Inner part of the thigh
What is the result of a femoral nerve lesion on knee extension?
Weakness of extension of the knee
what structures pass through the diapragm and at what level?
T8- IVC
T10- oesophagus and vagus
T12- Aorta and lymph ducts
